Quick and Dirty Hand Held "Tesla Coil"

Picture of Quick and Dirty Hand Held "Tesla Coil"
This is a very dangerous hand held high voltage generator. I built it from an auto ignition coil, power relay and a broken power drill. I call it a Tesla coil because that is what an ignition coil really is. It's a very convenient short cut to a high voltage spark generator.

You could build it with any power supply from 6 to 12 volts if you do not have a broken drill laying around.

This is a total hardware hack. I know it looks like crap. We were having a party and I wanted a prop that would scare people. I threw it together in about 2 hours. I've spent three times longer documenting the build than I did actually building it.

I have a really well stocked junk collection, so everything that I used to build this was actually laying around the shop before I started building it. The design is very flexible and will work with whatever junk you have.
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Step 1: The power source

Picture of The power source
I had a broken power drill. The trigger, PWM power control, and the battery were still fine. I removed the reversing switch, as the relay and coil only need one "direction".

I relocated the PWM power transistor to the side of the drill handle, because there was no room for it inside after the top of the handle broke off.

I attached two heavy (16 GA) wires to the power output of the drill speed control.

Step 2: The Filter

Picture of The Filter
Since there will be a lot of inductive kiickback voltage from the coil, I build a filter from two toroid coils and a large cap. The filter keeps the drill speed control from being blown out. The toroid coils had been salvaged from the input section of a dead power supply. The Cap was a random part that I had in my collection, any large cap over 25 volts and 4700uf or more will work here.

Step 3: The oscillating relay

Picture of The oscillating relay
This is a very simple circuit. The normally closed contacts of the relay power the relay coil. There is a 220uf cap across the relay coil. This cap need only be 16 volts or higher. When the relay pulls in it turns itself off. The cap provides enough energy storage to slow down the chatter of the contacts, and turn the relay from a buzzer to a slower oscillation. It has the advantage of not blowing out from the high voltage kickback from the coil.

The curly bits of wire serve as RF chokes and reduce radio frequency interference.

I put hot glue over the pins to insulate and protect them.

Step 4: The Coil

Picture of The Coil
This is a standard automobile replacement ignition coil. If you can, get one with an internal resistor. Mine did not have this, so I attached a ballast resistor to the side of the coil. The Resistor is needed to keep from "burning" the relay points.

Step 5: The probe

Picture of The probe
I used a piece of aluminum tubing from a hobby craft store for the central probe. I mounted the rod in a drill and turned it while holding sandpaper around it. This was used to round the tip and reduce the size o the rod to fit into the hot end of the coil.

I took a section of a spring and bent up the end of it until it was kinked and twisted. Then I forced this into the end of the coil with a twisting motion. This made a spring friction mount for the rod. The rod stays inside the spring really well.

Step 6: The Ground wires

Picture of The Ground wires
I used some tinned copper wire to make the ground wires. Each length of wire was placed over a 1/2 dowel rod. The ends of the wire were then mounted in a drill and turned until the two wires were tightly wrapped. Three of these were then mounted under the coil strap and then bent to about 3/4 inch from the probe tip.

The whole thing is pretty much held together with hot glue.

Step 7: Using it

Picture of using it
The battery charger still worked, so I can keep one battery in the charger while using the other. It lasts a long time on one charge, even though the batteries were used up and about useless when it was still a drill.

When the power is at a low setting, the relay points just chatter a little, but there is still several hundred volts at the probe. The power control has a low range, where the relay is chattering, and a high range, where the relay is getting a full stroke and the IGN coil is getting saturated.

There is an optimal setting of the "throttle". When you change the power level you are changing the "dwell" time of the relay points. The dwell is the time that the energy charges up in the winding before the points open and collapse the field. It is the abrupt collapse of the field that creates the high voltage flyback effect. The size of the spark gap also matters. If the gap is larger the voltage can ring up to a higher peak before it discharges. If the gap is too big, the air will never breakdown and there will be no arc. Remember that an arc in air is about 10,000 volts per centimeter, so I have seen as much as 45,000 volts from this coil.


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Jan_Henrik1 month ago

hehe, thats realy dirty, but nice project! ;)

makershaker052 months ago

What is the video called so I can search it on youtube, I will not play for me on the site

ben1233243 years ago
uuuuuuhhh... why does everyone call sparks a tesla coil? this is NOT an air core resonant transformer of any kind. it is cool, but just call it a high voltage gun or something
hardwarehacker (author)  ben1233243 years ago
Why does everyone think that Tesla only made air core transformers? The great one had a patent on the ignition coil, if anyone bothers to look it up...
An ignition coil is an air resonant transformer. Same setup as a TC without the tank circuit involved. He was very involved in distribution of power, and his primary focus was air resonance. He did improve some iron core transformer designs in his early career though.


actually a ignition coil has a iron core if anyone has took one apart

no, an ignition coil is not an air core. its a gapped iron core. tesla patented just about everything edison didn't steal from him, but that doesn't mean that everything he built that contains a coupled inductance is labeled "tesla coil" .

and aside from the rant, heres a REAL tesla coil gun if i've seen one. all credit to steve ward himself...
Dillon123 4 months ago

cool stun gun

TeslaBoy2 years ago
I tried the relay but even by changing the voltage to change the oscillation pattern the performance from my coil was still bad i was able to pull about a cm. I am hoping that a 555 timer with a hv diode and 2n3055 transistor will have a better effect
hardwarehacker (author)  TeslaBoy2 years ago
With this tuned right I have pulled over two inches from a standard car coil. You need to have a mass of metal on the secondary to tune it, that is the function of the rod that I put into the HV output. Different coils will need some tuning of the "top" mass and the primary capacitor. When it's working right there will be hundreds of volts from the primary flyback, so the 2n3055 will not survive that. if you clamp the flyback with a diode (like you would do with a relay) you will kill the ringing and not get the highest voltage.

There are lots of people saying "not a tesla coil" but the way I have this hooked up you have the issues as a big coil. It's not working as a simple transformer, but doing something like the resonant transfer of a air coil. This very high voltage from the ignition coil is coming from the disruptive arc on the primary and the ringing of the primary interacting with the secondary and the "top" mass. I have not seen this kind of voltage buildup with a transistor switched drive.
Thanks for the further information and to let you know your prediction happened instantly yet I anm just going to change the transistor to a MOSFET
hardwarehacker (author)  TeslaBoy2 years ago
For the maximum secondary voltage, the primary has to ring. This makes it very hard to drive with a solid state device, as the primary ringing will build up high voltages on the primary side. Be careful, as I blew out a nice power supply with this primary flyback while testing this the first time.
electronicz2 years ago
Could the relay be replaced by a P-channel JFET?

Like this:
hardwarehacker (author)  electronicz2 years ago
you could drive the coil with a transistor or MOSFET, but It would be easy to blow out a solid state switch. With a relay you get a bigger spark because of the "disruptive" arc in the primary.
Thanks, 5 stars
nerd74732 years ago
this is so cool i dont think may parents would let me build this
ilpug2 years ago
This can kill you.
pastaking2 years ago
One Word: PORTAL GUN! (Ok that's two, but "Two Words: PORTAL GUN!" doesn't sound as good!)
Could you also use the potentiometer on the Dewalt trigger control, to vary the output of a 555 timer? And get oscillations that way? I'm not sure myself, just a thought.
hardwarehacker (author)  CeasarVictus4 years ago
You could,but I like the raw, ragged chatter of the mechanical relay oscillator. (it's much more menacing than a tone)  Also using the relay this way there is nothing that can get blown out by the voltage spikes.
dude I love that chattering noise too, I used to hook up relays just to let them buzz old batteries dead lol

This would make a great 'steampunk' item with a little dressing up! Go for it!
shams3 years ago
Ahm...Its not a Tesla coil
That's why the name is in quotations...
hero 541233 years ago
would it be possible if i, make the coil shoot lightning farther,make the body longer and add rubber to it and make the wunder waffe DG2, from call of duty nazi zombies?
larch465 years ago
I go for long walks in the evenings with my wife, and I have always "worried" about a loose Rottweiler or any dangerous dog coming at us. As it is, we are totally unprotected. Is something like this viable for such a defense? I truly LOVE all animals, however when it comes to defending myself and my wife, I would consider something like this. We could wear a holster and only use it as a last course for sure.
There are self defense devices specifically for dogs that emit some kind of high pitch noise that will scare off dogs. Depending on where you live, you probably won't get attacked by a dog. If you do, take my Grandpa's advice: (he grew up in Yugoslavia and has had many encounters with stray dogs): "Kick at the legs, it is their weakest point."
Please don't use those ultra-sonic dog deterrents around me. They give me a nasty headache and make my teeth hurt. Now then, I am amazed by the sheer number of electrical geniuses haunting this site. I'd love to see someone organize a Tesla Fest for you guys. I imagine getting you together would be the first step towards a truly electrical which could run off it's own power and never need recharging. If anyone can do it, I imagine they are already members of this community.
Well, that would be nice, but it breaks the laws of Physics. You can't just make energy from energy, you have to lose some along the way. It's not so bad if you have to recharge. There just needs to be a more efficient way to produce electricity.
well energy can neither be created or destroyed so collect all the energy given off in the process of making the car move (heat, wind, movement, etc.) and to make up for loss that you can't collect collect surrounding energy (light, ambient heat, etc). To do this you could have magnets on every moving part of the vehicle surrounded by coils of wire on stationary parts that will act as frictionless generators, solar panels, and high efficiency wind turbines made from brushless motors which will have almost zero friction.  Another idea I have is, why don't we embedd magnets on all 50+ MPH roads alrenating which pole is facing up along the drive.  Under the vehicles have coils of copper wire running from the front to the back which will generate current as the vehicle drives over the magnents.  It will be an AC current which could use diodes as rectifiers to charge batteries to power electric motors or directly power the electric motors.  Of course the car would have to be made of a metal such as aluminum so that the magnets do not slow the car down but many electric cars today already have aluminum bodies like the tesla roadster.  any one feel free to take my ideas and put them to work because I am only 14 years old and can not afford the tools i would need to make this kind of technology work and I fear that before i could put my ideas to work a technology like this will already be invented.
I have to admit, I have had a similar idea to yours regarding the magnets in roads. My idea was to use the magnets to help propel the cars but your idea with using magnets to create currents on highways is way better. Keep looking into that.
Viz the magnets in the roads to generate electricity - you yourself have quoted that you cannot create energy, and this is what you would be doing... In order to generate current from the car's motion, you would apply a retarding force on the car, which the car would have to react against in order to continue at the same velocity. Thus all you are doing is burning more fuel to generate the electricity. And as no process is 100% efficient (thermodynamics, entropy, etc), it would be a waste - especially as there are far more efficient ways of converting chemical energy in fuel into electrical energy.

Sawry :/

PS I know this is an old post - but people are still reading it!
Energy can be neither created nor destroyed, but that doesn't particularly matter in this case. I think what Dzakovich000 meant was that energy in a system eventually becomes useless. For one thing, energy essentially cannot, in any practical system, be kept indefinitely in a closed system. However, more important is the first law of thermodynamics, a principle known as "entropy."

Entropy means that, in a given system, energy and matter tend towards the homogeneous. The law is "A system may not move from a disordered to an ordered state," essentially meaning that, in order for something as dispersed as heat to be collected and used from the top of a system, twice as much energy must be expended in conversion.

An example that might make this clearer, as it is essentially the same idea, is a perfectly heat-proof container, with a heater set in the bottom in a tub of water (converting electricity to heat) and a turbine halfway up (collecting heat as electricity, via generator). Though this might, at first glance, appear a perfect system, if the container is closed, then eventually the temperature will be completely uniform, and the turbine will stop turning; Heat will not spontaneously become another form of electricity, leaving a cold box again. This problem can be solved by opening the top of the container, but this presents two problems; The container is no longer heatproof, so not all of the energy produced is used, and you need to keep adding more water for steam.

This is the problem with all such systems. However, a car might be made (by no means cheaply) that, for example, has catches to turn to generators when going downhill without breaks (shutting off and leaving the battery undrained), solar panels along the top, and perhaps an emergency crank, which, if all is employed just right, might mean that it never has to be left to charge, but will charge while driving/parked.
That's a Bingo, Okapidragon!
nope this device is high voltage but not enough amperage to hurt much. a tesla coil is not a stun gun
Your comment is correct, however, this is not a Tesla Coil because it is not a RESONANT transformer, but rather an induction coil with a high turns ratio.
Xellers larch464 years ago
No, this device will not work for this purpose. It can give a somewhat surprising shock, but will not be effective at warding off any assailant once the surprise of the initial shock has worn off.
25cal colt pocket pistol
Dude, just buy a stun gun or some mace at the hard ware store. This is just to make pretty sparks :D
Limvot larch465 years ago
From the other comments, I would say yes. You might want to just get a tazer or something though I believe you need a license to carry one.
nope no license for a taser or stun gun at least in Virginia. we can even open carry firearms without a license. god i love Virginia.
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